Vaso-occlusive member assembly with multiple detaching points

ABSTRACT

This device is an apparatus for endovascular occlusion through the formation of thrombi in arteries, veins, aneurysms, vascular malformations, and arteriovenous fistulas. In particular, the device includes multiple vaso-occlusive members connected by electrolytically disintegratible links. Each link connects to the vaso-occlusive member by electrically insulative and conductive joints on opposite ends of the link. The vaso-occlusive members are delivered through a delivery catheter having on its distal end an electrode for electrical contact with the vaso-occlusive member. Upon application of an electrical current through the electrode to the vaso-occlusive member and its conductive joint to the electrolytically disintegratible link, the link disintegrates, selectively detaching the desired number of vaso-occlusive members into the target thrombus formation site.

RELATED PATENT APPLICATIONS

[0001] This application is a continuation of U.S. patent applicationSer. No. 09/330,462, filed Jun. 11, 1999, which is a continuation ofU.S. patent application Ser. No. 09/025,707, filed Feb. 18, 1998, nowU.S. Pat. No. 5,941,888; the entirety of each is hereby incorporated byreference.

FIELD OF THE INVENTION

[0002] This invention generally relates to the delivery of an occlusiondevice to a desired site in a mammal to facilitate the formation ofmechanical blockage or thrombi in arteries, veins, aneurysms, vascularmalformations and arteriovenous fistulas. More specifically, theinvention involves one or more vaso-occlusive members that can besequentially and selectively delivered by electrolytic detachment of asacrificial link to a desired thrombus formation site. This inventionpermits a physician effectively to select the length of a vaso-occlusivedevice for delivery to a selected site without removing the deliverywire from the delivery catheter.

BACKGROUND OF THE INVENTION

[0003] Approximately 25,000 intracranial aneurysms rupture each year inNorth America. The primary purpose of treatment for a rupturedintracranial aneurysm is to prevent rebleeding. There are a variety ofways to treat ruptured and non-ruptured aneurysms.

[0004] Possibly the most widely known of these procedures is anextravascular approach using surgery or microsurgery. This treatment iscommon with intracranial berry aneurysms. The method comprises a step ofclipping the neck of the aneurysm, performing a suture ligation of theneck, or wrapping the entire aneurysm. Each of these procedures isformed by intrusive invasion into the body and performed from theoutside of the aneurysm or target site. General anesthesia, craniotomy,brain retraction, and placement of a clip around the neck of theaneurysm are typically required in these surgical procedures. Thesurgical procedure is often delayed while waiting for the patient tostabilize medically. For this reason, many patients die from theunderlying disease or defect prior to the initiation of the procedure.

[0005] Another procedure—the extra-intravascular approach—involvessurgically exposing or stereotactically reaching an aneurysm with aprobe. The wall of the aneurysm is then perforated from the outside andvarious techniques are used to occlude the interior in order to preventit from rebleeding. The techniques used to occlude the aneurysm includeelectrothrombosis, adhesive embolization, hog hair embolization, andferromagnetic thrombosis. These procedures are discussed in U.S. Pat.No. 5,122,136 to Guglielmi et al., the entirety of which is incorporatedby reference.

[0006] A still further approach is the least invasive and isadditionally described in Guglielmi et al. It is the endovascularapproach. In this approach, the interior of the aneurysm is entered byuse of a catheter such as those shown in U.S. Pat. Nos. 4,884,575 andU.S. Pat. No. 4,739,768, both to Engelson. These patents describedevices utilizing core wires and catheters, respectively, which allowaccess to the aneurysm from remote portions of the body. By the use ofcatheters having very flexible distal regions and core wires which aresteerable to the region of the aneurysm, embolic devices which may bedelivered through the catheter are an alternative to the extravascularand extra-intravascular approaches.

[0007] The endovascular approach typically includes two major steps. Thefirst step involves the introduction of the catheter to the aneurysmsite using catheters such as shown in the Engelson patents. The secondstep often involves filling the aneurysm in some fashion or another. Forinstance, a balloon may be introduced into the aneurysm from the distalportion of the catheter where it is inflated, detached, and left toocclude the aneurysm. In this way, the parent artery is preserved.Balloons are becoming less favorable because of the difficulty inintroducing the balloon into the aneurysm sac, the possibility of ananeurysm rupture due to overinflation of the balloon within theaneurysm, and the risk associated with the traction produced whendetaching the balloon.

[0008] A highly desirable embolism-forming device which may beintroduced into an aneurysm using endovascular placement procedures isfound in U.S. Pat. No. 4,994,069 to Ritchart et al. The device,typically a platinum/tungsten alloy coil having a very small diameter,may be introduced into an aneurysm through a catheter such as thosedescribed in Engelson above. These coils are often made of wire having adiameter of 2-6 mils. The coil diameter may be 10-30 mils. These soft,flexible coils may be of any length desirable and appropriate for thesite to be occluded. For instance, the coils may be used to fill a berryaneurysm. Within a short period of time after the filling of theaneurysm with the embolic device, a thrombus forms in the aneurysm andis shortly thereafter complemented with a collagenous material whichsignificantly lessens the potential for aneurysm rupture. Coils such asthose seen in Ritchart et al. may be delivered to the vasculature sitein a variety of ways including, e.g., mechanically detaching them fromthe delivery device as is shown in U.S. Pat. No. 5,250,071 to Palermo,or by electrolytic detachment as is shown in Guglielmi et al. (U.S. Pat.No. 5,122,136) as discussed above.

[0009] Guglielmi et al. teaches an embolism-forming device and procedurefor using that device. Specifically, Guglielmi et al. fills a vascularcavity such as an aneurysm with an embolic device such as a platinumcoil which has been endovascularly delivered. The coil is then severedfrom its insertion tool by the application of a small electric current.Desirably, the insertion device involves a core wire which is attachedat its distal end to an embolic device by an electrolytic, sacrificialjoint. Guglielmi et al. suggests that when the embolic device is aplatinum coil, the coil may have a length ranging from 1 cm to 50 cm orlonger as is necessary. Proximal of the embolic coil is an insulatedcore wire or pusher wire, often stainless steel in construction. Thecore wire is used to push the platinum embolic coil, obviously withgreat gentleness, into the vascular site to be occluded. The Guglielmiet al. patent shows a variety of ways to link the embolic coil to thecore wire. For instance, the core wire is tapered at its distal end andthe distal tip of the core wire is welded into the proximal end of theembolic coil. Additionally, a stainless steel coil is wrapped coaxiallyabout the distal tapered portion of the core wire to provide columnstrength to the core wire. This coaxial stainless steel wire is joinedboth to the core wire and to the embolic coil. Insulation may be used tocover a portion of the strength-providing stainless steel coil. Thisarrangement provides for two regions which must be electrolyticallysevered before the embolic coil is severed from the core wire.

[0010] A still further variation found in Guglielmi et al. includes athin, threadlike extension between the core wire core and the proximalend of the embolic coil. In this way, the core wire does not extend tothe embolic coil, but instead relies upon a separately introducedextension.

[0011] A continuation-in-part of the Guglielmi et al. patent discussedabove, U.S. Pat. No. 5,354,295, describes the use of mechanicallydetachable embolic devices as well as those which are electrolyticallydetachable. The embolic devices may be augmented with attachedfilaments. U.S. Pat. No. 5,540,680, a continuation of U.S. Pat. No.5,354,295, further describes such mechanically and electrolyticallydetachable embolic devices. U.S. Pat. No. 5,569,245, acontinuation-in-part of the 5,540,680 patent, adds several new aspectsincluding a new method for electrocoagulation.

[0012] A further variation of the Guglielmi et al. device is one inwhich the distal tip of the stainless steel core wire is crimped ontothe proximal end of the embolic device. A simple tapered stainless steelwire extends from the stainless steel pusher wire to the embolic coil.

[0013] Taki et al. have devised a variation of the Guglielmi detachablecoil using a copper link between the core wire and the coil, describedin Treatment of a Spontaneous Carotid Cavernous Fistula Using anElectrodetachable Microcoil, American Journal of Neuroradiology, Vol. 14(1993).

[0014] U.S. Pat. Nos. 5,423,829 and 5,624,449, both to Pham et al.,describe an electrolytically detachable vaso-occlusive device containinga discrete sacrificial link between the core wire and the vaso-occlusivedevice to allow clean and quick detachment from the core wire, reducingthe possibility of multiple electrolysis sites. The use of extensiveelectrical insulation about the core wire and sacrificial link as wellas the use of scoring on the insulation to focus electrolysis on atargeted, specific site on the link is also taught by Pham et al.

[0015] In order to tailor the length of the vaso-occlusive member duringimplantation so to effectively treat the aneurysm, U.S. Pat. No.5,522,836 to Palermo discloses a vaso-occlusive device such as a coil inwhich the length of the coil can be tailored during the procedure. Thisis accomplished by the use of an electrode which is movable relative tothe vaso-occlusive coil.

[0016] U.S. Pat. No. 5,312,415 to Palermo teaches another device thatenables more accurate placement of a vaso-occlusive coil. In thisdevice, a catheter having a constricted or feathered distal end toretain vaso-occlusive coils on a core wire, allowing the delivery of anumber of coils loaded on one pusher, thereby eliminating the need toremove the core wire from the catheter and re-insert it between coildeliveries.

[0017] None of the disclosed devices suggests the use of a vascularocclusion member assembly in which multiple vaso-occlusive devices canbe selectively detached via multiple electrolytically disintegratiblelinks.

SUMMARY OF THE INVENTION

[0018] This invention is a device for forming a vascular occlusion at aselected site. Generally, the device comprises a vaso-occlusive memberhaving an electrically insulative joint located proximally on thevaso-occlusive member, an electrolytically disintegratible link locatedproximally of the insulative joint, and an electrically conductiveregion, which may be a section of conductive vaso-occlusive material,proximal of the link which connects to an additional vaso-occlusivemember. In conjunction with this assembly is a delivery catheter havingan integral distal electrode configured for electrical contact with theelectrically conductive region of the vaso-occlusive members. Thesevaso-occlusive members may be placed nose-to-tail. Upon application ofelectric current to the electrically conductive region, a nearbyelectrolytically disintegratible link disintegrates, releasing a portionof the assembly. The presence of multiple disintegratible links,typically separated from each other by insulative joints, allows theplacement of a selected number of vaso-occlusive members into thetherapeutic site as the physician chooses. An alternative variationutilizes two catheters, one for delivering one or more vaso-occlusivemembers, the other for deploying an electrode for electrolyticallydetaching the desired number of vaso-occlusive members by disintegratingone of the links.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 is a cross-sectional view of one variation of thevaso-occlusive member assembly of the present invention.

[0020]FIG. 2 is the vaso-occlusive member assembly in conjunction with adelivery catheter containing an electrode.

[0021]FIG. 3 is a cross-sectional view of the distal end of a cathetercontaining an alternative electrode arrangement.

[0022]FIGS. 4A and 4B are cross-sectional and perspective views,respectively, of the distal end of a catheter containing anotheralternative electrode arrangement.

[0023]FIG. 5 schematically depicts the method of deploying thevaso-occlusive member assembly of the present invention into a vascularaneurysm.

[0024]FIG. 6 is an alternative variation of the present invention inwhich a second catheter containing an electrode is used for detachingthe vaso-occlusive member.

DETAILED DESCRIPTION OF THE INVENTION

[0025] An artery, vein, aneurysm, vascular malformation or arterialfistula is occluded through endovascular occlusion by the endovascularinsertion of a vaso-occlusive member into the vascular cavity. Becauseof the unique design of the present invention, the appropriate lengthvaso-occlusive member or members can effectively be selected by thephysician without removal of the delivery wire from the deliverycatheter.

[0026]FIG. 1 shows the basic vaso-occlusive assembly 100 of the presentinvention. The term “proximal” generally refers to the right side andthe term “distal” generally refers to the left side of the figures inthis document. Distal vaso-occlusive member 102 and proximalvaso-occlusive member 104 are shown as helical coils, although they maybe any other suitable device or form, such as a ribbon, a braidedmember, or the like. Vaso-occlusive members 102 and 104 should be of asize sufficiently small that they may be advanced through a catheter(not shown) that is appropriately sized for accessing the targetedvascular site. For instance, when accessing a brain aneurysm in a smallvessel, an appropriately sized catheter is quite small and veryflexible. The vaso-occlusive member in such a situation must be smallenough to fit through the catheter and out its distal end at thetreatment site. Optionally, vaso-occlusive members 102 and 104 may beelongated, depending upon the form the vaso-occlusive member takes. Forinstance, if vaso-occlusive members 102 and 104 are in the form of coilsas shown in FIG. 1, they may be elongated by containing an increasednumber of total windings from their proximal to distal ends. As shown inFIG. 1, vaso-occlusive assembly 100 can consist of multiplevaso-occlusive members 102 and 104. Additionally, assembly 100 mayconsist of any number of vaso-occlusive members, depending on thespecific treatment desired by the physician.

[0027] Vaso-occlusive members 102 and 104 are desirably made up of aradiopaque, physiologically compatible material. Suitable metals andalloys for the wire making up those regions include the Platinum Groupmetals, especially platinum, rhodium, palladium, rhenium, as well astungsten, gold, silver, tantalum, and alloys of these metals. Thesemetals have significant radiopacity and in their alloys may be tailoredto accomplish an appropriate blend of flexibility and stiffness. Theyare also largely biocompatible. Highly preferred is a platinum/tungstenalloy, e.g., 8% tungsten and the remainder platinum.

[0028] Certain polymers are also suitable as vaso-occlusive membermaterial either alone or in conjunction with metallic markers to provideradiopacity. These materials are chosen so that the procedure oflocating the vaso-occlusive member within the vessel may be viewed usingradiography. However, it is also contemplated that the vaso-occlusivemembers may be made of various other biocompatible polymers or of carbonfibers. The vaso-occlusive device may be covered or connected withfibrous materials tied to the outside of the coil or braided onto theouter cover of the coil as desired. Such fibrous adjuvants may be foundin U.S. Pat. Nos. 5,354,295 to Guglielmi et al., 5,382,259 to Phelps etal., or 5,226,911 to Chee et al.; the entirety of each are incorporatedherein by reference. The particular form and choice of material used forthe vaso-occlusive members will of course depend on the desiredapplication. It is preferred that at least one of the vaso-occlusivemembers be electrically conductive so to make possible electrolyticseparation of the assembly as will be described below.

[0029] When one or more of the vaso-occlusive members is a coil, itsshape and constituent winding will depend upon the use to which the coilwill be placed. For occluding peripheral or neural sites, the coils willtypically be made of 1 mil to 5 mil diameter wire (platinum orplatinum/tungsten alloy) that may be wound to have an inner diameter of5 mils to 60 mils with a minimum pitch—that is to say that the pitch isequal to the diameter of the wire used in the coil. The outer diameteris then typically between 0.007 and 0.700 inch.

[0030] The length of the coil will normally be in the range of 0.5 to 60cm, preferably 0.5 to 40 cm. As discussed in conjunction with FIG. 2below, any number of vaso-occlusive devices may be used in the presentinvention, subject to considerations of safety, the length of the coilschosen, the therapy being administered by the attending physician, andthe desire to maintaining the overall optimal stiffness of thevaso-occlusive member assembly. When, for instance, the vaso-occlusivemembers are coils, anywhere from two to twenty coils may be used, with apreferable number being two to ten, and an even more preferable numberbeing two to five. Balancing the tendency for the overall stiffness ofthe joined coil assembly to increase with additional coils versus safetyand other considerations is critical in determining the optimal numberof coils or other vaso-occlusive members to be used in the presentinvention.

[0031] If desired, the coils may be formed in such a way that they areessentially linear as they pass through the catheter and yet assume arandomly oriented relaxed condition after they are released from thedistal end of the catheter. A discussion of this variation may be foundin U.S. Pat. No. 4,994,069 to Ritchart et al.

[0032] Electrolytically disintegratible link 106 is shown betweenvaso-occlusive members 102 and 104 in FIG. 1. Link 106 is preferablybare and is relatively more susceptible to electrolysis in an ionicsolution such as blood or most other bodily fluids than isvaso-occlusive members 102 and 104. Alternatively, link 106 may betapered or otherwise modified, or coated with an insulative polymer andscored, such as described in U.S. Pat. No. 5,624,449 to Pham et al., theentirety of which is incorporated herein by reference, to limit the areaof electrolytic disintegration of link 106 to a more discrete region orpoint. For all figures herein, the electrolytically disintegratible linkmay take the form of a straight member (as shown in FIG. 1 for link106), or it may take the form of other shapes; for example, a coil. Oneadvantage of having link 106 take the form of a coil is that thisconfiguration would help preserve the uniform diameter of vaso-occlusivemembers 102 and 104.

[0033] Central to this invention is electrical isolation ofvaso-occlusive members 102 and 104 by electrically insulative joint 108,which joins the proximal end of vaso-occlusive member 102 to link 106.Without wishing to be bound by theory, it is believed that electricalisolation of vaso-occlusive members 102 and 104 prevents or lessenscurrent flow through the vaso-occlusive members and concentrates thecurrent flow through link 106. Preferably, as shown in FIG. 1,insulative joint 108 surrounds link 106 and is contained within thelumen defined by vaso-occlusive member 102.

[0034] Insulative joint 108 serves two primary functions. The first isto electrically insulate link 106 from vaso-occlusive member 102 so thatelectrical energy is not transmitted from the link to vaso-occlusivemember or any part of the assembly of the present invention distal tothe particular link 106 selected for electrolytic disintegration. Thesecond is to reliably and fixedly join link 106 to vaso-occlusive member102.

[0035] Preferably, electrically insulative joint 108 is comprised of abiocompatible, electrically insulative material such aspolyfluorocarbons (e.g. TEFLON), polyethylene terepthalate,polypropylene, polyurethane, polyimides, polyvinylchloride, and siliconepolymers.

[0036] In addition to the polymers listed above, another desirablematerial is generically known as parylene. There are a variety ofpolymers (e.g., polyxylylene) based on para-xylylene. These polymers aretypically placed onto a substrate by vapor phase polymerization of themonomer. Parylene N coatings are produced by vaporization of adi(P-xylylene) dimer, pyrolization, and condensation of the vapor toproduce a polymer that is maintained at a comparatively lowertemperature. In addition to parylene-N, parylene-C is derived fromdi(monochloro-P-xylylene) and Parylene-D is derived fromdi(dichloro-P-xylylene). There are a variety of known ways to applyparylene to substrates. Their use in surgical devices has been shown,for instance, in U.S. Pat. Nos. 5,380,320 (Morris), 5,174,295 (Christianet al.), 5,067,491 (Taylor et al.), and the like.

[0037] Alternatively, thermoplastic materials such as those disclosed inU.S. Pat. No. 5,944,733 to Engelson, the entirety of which is herebyincorporated herein by reference, are contemplated for use as adhesivesin comprising insulative joint 108 in the present invention, alone or incombination with the other polymers herein described.

[0038] The thermoplastic, polymer or combination of such used tocomprise insulative joint 108 may be formed in any number of ways. Onetechnique, for example, is dipping or coating link 106 in a molten orsubstantially softened polymer material, but other techniques as knownin the art, such as shrink-wrapping, line-of-sight deposition in theform of a suspension or latex, or others may be used as well.

[0039] Another material that may be used for electrically resistiveinsulative joint 108, alone or in combination with one or morethermoplastic or polymer layer, is a biocompatible and electricallyresistive metallic oxide. Oxides with a high dielectric constant, suchas those of tantalum or titanium or their alloys, are preferred, withthe various oxides of tantalum as most preferred. Such oxides can beformed in any number of ways. For example, they may be in the form of adeposited film, such as that made by plasma deposition of the base metal(e.g., in elemental or alloy form), or they may exist in the form of asleeve or hypotube of the base metal that is welded, brazed, soldered,mechanically joined, or otherwise fixed to link 106. This base metallayer can then be subsequently oxidized (by imposition of theappropriate electrical current or other such excitation, such as bywelding during assembly of the device) to form the desired electricallyinsulative oxide layer. Alternatively, the oxide may be depositeddirectly in oxide form by any number of techniques that does not requiresubsequent oxidation of the base metal in elemental or alloy form.

[0040] Whether electrically insulative joint 108 is comprised of amonolithic layer of a single polymer or thermoplastic, multiple layersof various polymers or thermoplastics, or an electrically insulativemetallic oxide (alone or in combination with any number of polymers orthermoplastics), its thickness (as measured radially outward from thesurface of link 106 towards vaso-occlusive member 102) can range from0.002 inch to 0.040 inch, with 0.001 inch to 0.018 inch being preferredand 0.003 inch to 0.0010 inch as most preferred. It is preferred thatthe total thickness of insulative joint 108 be no greater than 0.060inch (or, alternatively, no greater than the inner diameter ofvaso-occlusive member 102 and no less than the minimum to allowinsulative joint 108 to perform its intended functions of joining andelectrically insulating vaso-occlusive member 102 and link 106.

[0041] The optimal thickness of each layer will depend on the desiredthermal, electrical and mechanical properties of the insulative joint108, the types and combinations of materials used, dimensionalconstraints relative to link 106 and vaso-occlusive member 102, andmanufacturing, engineering, cost and other factors as well. Forinstance, the thickness of insulative joint 108 can range from one or afew hundred angstroms (for example if an oxide layer was used) to asthick as the remaining inner diameter of the vaso-occlusive member 102(for example if a polymer or thermoplastic was used), taking intoconsideration the diameter of link 106, in which it is positioned. Thislatter thickness is especially desirable from a manufacturing standpointas the insulative joint 108 most readily serves its two aforementionedfunctions of electrical insulation and joining.

[0042] Insulative joint 108 may join vaso-occlusive member 102 to link106 by any number of various techniques. For example, joint 108 may beformed by an interference, or friction, fit. Alternatively, insulativejoint 108 can be formed by line-of-sight deposition methods while link106 and vaso-occlusive member 102 are aligned in the desired position sothat as link material is deposited, it “fixes” the link 106 andvaso-occlusive member 102 into a locked position relative to oneanother.

[0043] Proximal of link 106, electrically conductive joint 110 joins thedistal end of vaso-occlusive member 104 to link 106. Preferably, asshown in FIG. 1, conductive joint 110 surrounds link 106 and iscontained within the lumen defined by vaso-occlusive member 104.

[0044] Conductive joint 110 serves two primary functions. The first isto provide an electrical pathway between link 106 from vaso-occlusivemember 104 so that electrical current is readily transmitted betweenthese two members. The second is to reliably and fixedly join link 106to vaso-occlusive member 104.

[0045] Conductive joint 110 can be made from any biocompatible,electrically conductive material, preferably a suitable metal such asplatinum or stainless steel hypotubing. In addition, a superelasticmaterial such as nitinol may be used if desired; however, care must betaken in this case to keep it free from surface oxidation prior tofixing the joint 110 to the coil (such as by fabrication in asubstantially oxygen-free environment or by plating the joint 110 with aconductive metal such as, for example, gold, silver, etc.). Ifconductive joint 110 comprises a stainless steel hypotube, the joint maybe assembled by welding, brazing, soldering, mechanically joining (as bycrimping, for example) or otherwise connecting a hypotube having a wallthickness appropriate to join link 106 and vaso-occlusive member 104 toproximal end of link 106. This hypotube is then welded, brazed,soldered, or otherwise fixed to vaso-occlusive member 104.

[0046]FIG. 2 shows, in partial cross-section, a series of vaso-occlusivemembers as described according to FIG. 1 in cooperation with the distalend of a catheter 202 having distal electrode 204 similar to thatdescribed in U.S. Pat. No. 6,059,779 to Mills, the entirety of which isincorporated by reference.

[0047] Preferably, and as described in U.S. Pat. No. 6,059,779, catheter202 comprises an elongated tubular member or tube having a laminatestructure comprising a pair of concentrically arranged tubular membersor tubes 206 and 208. The inner surface or wall of first tube 206defines lumen 210 through which the vaso-occlusive members, numberedgenerally as 212, are passed. Other catheter constructions may be usedwithout departing from the scope of the invention.

[0048] Catheter 202 is preferably equipped with an annular distalelectrode 204, partially embedded between first tube 206 and second tube208, as shown in FIG. 2. Electrode 204 may comprise any conductivebiocompatible material. For example, electrode 204 may compriseconductive metals and their alloys (for example, steel, titanium,copper, platinum, nitinol, gold, silver or alloys thereof), carbon(fibers or brushes), electrically conductive doped polymers or epoxies,or any combination thereof. In this variation, electrode 204 and tubes206 and 208 are preferably designed so that the electrode 204 andcatheter lumen 210 present a continuous, nonobstructed, smooth surfaceto allow vaso-occlusive member 212 to pass smoothly out of the distalend of catheter 202. Such an annular construction maximizes theelectrode's exposed surface area so to increase current flowefficiencies by avoiding too large a current density passingtherethrough. Finally, it is preferred in this variation that distalsurface 214 of electrode 204 is substantially flush with the distalsurface 216 of catheter 202. However, other configurations wherein theelectrode 204 is spaced inwardly from the distal surface 216 of catheter202 to eliminate or minimize interference with other vaso-occlusivemembers, as disclosed in U.S. Pat. No. 6,059,779, is also within thescope of this invention. In the case where electrode 204 is spacedinwardly, it is preferred that the maximum offset from the distalsurface 216 of catheter 202 be the distance between electrolyticallydisintegratible links 224. Likewise, configurations in which electrode204 is spaced outwardly from the distal surface 216 of catheter 202 toensure conductive contact with vaso-occlusive member 212 may also beused.

[0049] Catheter 202 is further provided with a conductor 218. As shownin FIG. 2, conductor 218 is in the form of an annular extension ofelectrode 204. Alternatively, conductor 218 can be in the form of a wireor ribbon whose distal end is coupled, for example by welding, toelectrode 204. Conductor 218 extends from electrode 204 between tubularmembers 206 and 208 to proximal end portion of catheter 202 where it canbe electrically connected to a power supply either directly or with alead as would be apparent to one of ordinary skill in the art.

[0050] Vaso-occlusive members 212 are as described above in conjunctionwith FIG. 1. Accordingly, each is provided on its proximal end with anelectrically insulative joint 222 joining vaso-occlusive member 212 toelectrolytically disintegratible link 224. Likewise, link 224 is affixedto the distal end of vaso-occlusive member 212 via electricallyconductive joint 226 as described above. The most proximal ofvaso-occlusive members 212, which in FIG. 2 is depicted as locatedwithin the lumen 210 of catheter 202, is connected to a core wire 228via electrically insulative joint 222. This core wire 228 is used by thephysician to advance the series of vaso-occlusive members 212 throughthe catheter lumen and to the desired therapeutic site as is well-knownin the art.

[0051] Although the configuration of insulative joint 222 being distalto conductive joint 226, as shown in FIG. 2, is preferable, it is alsowithin the scope of this invention to switch the respective locations ofthese elements so that insulative joint 222 lies proximal to conductivejoint 226. In this latter alternative configuration, detachment willoccur by electrolytic dissolution of a link 224 that is positionedproximal of electrode 204.

[0052] An alternative electrode-catheter configuration is shown in crosssection in FIG. 3. In this variation, conductor 300 is connected to, orcan be an integral part of, electrode 302. Electrode 302 is partiallycovered and conductor 300 is completely covered on the inner diameter ofcatheter 304 with an electrically insulative covering 306. This coveringserves to electrically isolate conductor 300 and all but a distalsection of electrode 302 from the lumen of catheter 304, as well as toprovide a continuous, nonobstructed, smooth surface to allowvaso-occlusive members (not shown) to pass smoothly out of the distalend 308 of catheter 304. Electrically insulative covering 306 may becomprised of an electrically insulative polymer or polymers as describedabove, and may additionally or singly comprise an electricallyinsulative metallic oxide such as tantalum oxide or the like. In thisconfiguration, conductor 300 may, for example, be a metallic braid,while electrode 302 may, for example, be a platinum or platinum alloyhypotube. Of course, conductor 300 and electrode 302 can take otherforms or configurations. Electrode 302 may also extend beyond the distalend 308 of catheter 304 to ensure electrical contact with vaso-occlusivemembers.

[0053] It is within the scope of this invention for the electrode totake on other forms, for example, a tubular braided structure such asdescribed in U.S. Pat. No. 6,059,779. A braided configuration has theadvantage of allowing the designer to vary the stiffness of the catheterby varying the mesh size of the braid along the length of the catheter.

[0054] Although FIG. 3 shows electrode 302 to be substantially flushwith the distal surface 308 of catheter 304, electrode 302 can be spacedinwardly from the distal surface 308 of catheter 304 to eliminate orminimize interference with other vaso-occlusive members. Likewise,electrode 302 can be spaced outwardly from the distal surface 308 ofcatheter 304 to ensure conductive contact with a vaso-occlusive member.

[0055] Turning now to FIGS. 4A and 4B, yet another variation of theelectrode design which additionally accommodates vaso-occlusive membersof different sizes is presented. In this configuration, the electrodeconsists of one or more radial extensions 402 located near the distalend of catheter 404. Radial extensions 402 extend radially towards thecenter of the catheter lumen from an electrically connected embeddedconductor 406. Extensions 402 can be arranged symmetrically along thecircumference of catheter 404 as shown in FIGS. 4A and 4B, or they maybe arranged asymmetrically depending on the design of the invention.Although four extensions 402 are shown in FIGS. 4A and 4B, it isanticipated that from 1 to 10 extensions can exist in the distal end ofcatheter 404.

[0056] Extensions 402 can comprise any electrically conductive material,as discussed before, such as stainless steel, platinum, or nitinol, forexample. It is important that extensions 402 be comprised of a materialthat has a relatively high degree of flexibility to allow passage ofvaso-occlusive members (not shown) through the distal end of catheter404 while being stiff enough to maintain electrical contact with thevaso-occlusive members so that electrical energy can be transmitted tothe electrolytically disintegratible link (not shown).

[0057] Additionally, FIGS. 4A and 4B shows a preferred configuration forextensions 402. In this variation, extensions 402 are disposed at anacute angle α as measured from the catheter inner surface on the distalside of extension 402. This design facilitates passage of vaso-occlusivemembers out through the distal end of catheter 404 and into thetherapeutic site, while simultaneously hindering motion in the oppositedirection back into the lumen of catheter 404. It is contemplated thatextensions 402 can be disposed at an angle α which is acute or even, insome cases, ninety degrees or slightly obtuse.

[0058] Extensions 402 can be in the form of ribbons, for example, thatare welded, brazed, soldered, glued, or otherwise electrically andfixedly attached to conductor 406. Extensions 402 may also be anintegral part of conductor 406. For example, extensions 402 can be cutfrom a nitinol hypotube on three sides and bent to the desired angle αalong the still-intact fourth side which joins the hypotube. Thishypotube can then be assembled with catheter 202. Alternatively,extensions 402 can be formed from one or more coils.

[0059]FIG. 5 shows placement of a vaso-occlusive member 502 of thepresent invention within a vessel 504 with the distal end of catheter506 placed near neck 508 of aneurysm 510. Conventional catheterinsertion and navigational techniques involving core wires orflow-directed devices may be used to access the aneurysm 510. Once thedistal end of catheter 506 is positioned at the site, often by locatingits distal end through the use of radiopaque marker material andfluoroscopy, the catheter is cleared. For instance, if a core wire hasbeen used to position the catheter, it is withdrawn from the catheterand then the core wire 512 having any number of vaso-occlusive members502 at the distal end is advanced through the catheter. The core wire512 is advanced so that the link 522 to be electrolytically severed isjust outside the distal end of catheter 506 and is in electrical contactwith the electrode 514 through conductive joint 516. To assist thephysician in positioning the desired link 522 to be electrolyticallydetached, radiopaque marker 524 can be used. Because differentocclusions, such as aneurysm 510, will require varying amounts ofvaso-occlusive material for proper treatment, it may be necessary todeploy multiple vaso-occlusive members 522 into aneurysm 510. With theassistance of radiopaque marker 524, the physician can selectivelydeploy one or more vaso-occlusive member 502 into the aneurysm 510 asrequired until the aneurysm 510 has been sufficiently filled.

[0060] This marker 524, which is preferably comprised of a platinumhypotube, is embedded in catheter 506 and spaced proximally from thedistal end of catheter 506 a distance that corresponds to the spacingbetween link 522 and link 526. Vaso-occlusive members 502 preferably areradiopaque while links 522 and 526 preferably are not.

[0061] When used in combination with electrode 514 (which can serve asor can additionally contain a radiopaque marker to indicate the distalend of catheter 504), a physician positions wire 512 so that link 526 iscentered under radiopaque marker 524 as shown in FIG. 5. By doing so,the physician will know that the next most distal link 522 is positionedjust distal of electrode 514 (through conductive joint 516) and thatelectrolytic detachment will occur at distal link 522.

[0062] Depending on constraints such as the condition and size of theocclusion, the physician may desire to use vaso-occlusive members 502 ofvarying length. Therefore, it is contemplated that catheter 504 cancontain multiple radiopaque markers 524, each positioned in from thedistal end of catheter 504 a distance corresponding to the spacingbetween links that separate vaso-occlusive members of varying length.This will give the physician maximum flexibility in accurately,reliably, and safely deploying any number of vaso-occlusive members ofidentical or varying lengths, singly or in combination, into the site tobe occluded.

[0063] A positive electric current of approximately 0.01 to 2 milliampsat 0.1 to 6 volts is next applied to core wire 512 by power supply 518to form a thrombus within aneurysm 510. Typically, the negative pole 520of power supply is placed in electrical contact with the skin.

[0064] After the thrombus has been formed and the aneurysm occluded,link 522 just distal of electrode 514 is electrolytically disintegrated,detaching the desired number of vaso-occlusive devices from core wire512.

[0065] After link 522 is completely dissolved or eroded by electrolyticaction, typically within 0.5 to 10 minutes, the core wire 512 andcatheter 506 are removed from vessel 504, leaving aneurysm 510 occluded.

[0066] Finally, FIG. 6 illustrates an alternative variation of theinventive device as used in a mammal vasculature (not shown). In thisconfiguration, catheter 602 containing core wire (not shown) andvaso-occlusive member 606 does not contain an electrode. A secondmicrocatheter 608 containing an electrode 610 is used to access anexposed electrolytically disintegratible link 612 or vaso-occlusivemember 606 to electrolytically disintegrate link 612 and detachment ofthe desired number of vaso-occlusive members 606 into the therapeuticsite.

[0067] Although shown in FIG. 6 as an elongated wire, electrode 610 maytake any number of forms as long as it effectively transmits electriccurrent to a vaso-occlusive member 606 or link 612. Additionally,although first catheter 602 is shown in FIG. 6 as not having anelectrode, this is not required. For example, a dual-catheter system inwhich the first catheter 602 contains an electrode that has becomeinoperative is within the scope of the invention.

[0068] Many alterations and modifications may be made by those havingordinary skill in the art without departing from the spirit and scope ofthe invention. The illustrated variations have been used only forillustration and clarity and should not be taken as limiting theinvention as defined by the following claims.

We claim the following:
 1. An assembly for use in the formation of anocclusion comprising: an occlusive member having a proximal end, aninsulative joint located proximally on said occlusive member, anelectrolytically disintegratible link located proximally of saidinsulative joint, and a conductive joint located proximally on saidelectrolytically disintegratible link, said joint configured forconnection to an additional occlusive member.
 2. The assembly of claim 1wherein said link is coated with an insulative layer containing agroove, said groove exposing said underlying link.
 3. The assembly ofclaim 2 wherein said insulative layer comprises a polymer.
 4. Theassembly of claim 3 wherein said groove is produced by laser scoring. 5.The assembly of claim 1 wherein said occlusive member comprises a coil.6. The assembly of claim 1 wherein said insulative joint is saidinsulative layer.
 7. The assembly of claim 1 wherein the insulativejoint comprises an electrically insulative biocompatible adhesive.
 8. Anassembly for use in the formation of an occlusion comprising: avaso-occlusive member having a proximal end and a distal end, aninsulative joint disposed on said proximal end of said vaso-occlusivemember, and a conductive joint disposed on said distal end of saidvaso-occlusive member.
 9. The vaso-occlusive member of claim 8additionally comprising an electrolytically disintegratible link locatedproximally of said insulative joint.
 10. The vaso-occlusive member ofclaim 8 wherein said vaso-occlusive member is a coil.
 11. The assemblyof claim 10 wherein said link is coated with an insulative layercontaining a groove, said groove exposing said underlying link.
 12. Theassembly of claim 11 wherein said insulative layer comprises a polymer.13. The assembly of claim 12 wherein said groove is produced by laserscoring.
 14. The assembly of claim 8 wherein the insulative jointcomprises an electrically insulative biocompatible adhesive.
 15. Amethod for occluding a body cavity, comprising: disposing an assembly atleast partially into said body cavity, said assembly comprising (i) awire having a first insulative joint attached to a distal end of saidwire, a first vaso-occlusive member attached to said first insulativejoint, and (ii) at least one section comprising (1) a conductive jointattached to said first vaso-occlusive member, (2) an electrolyticallydisintegratible link having a proximal end attached to said conductivejoint and a distal end attached to an additional insulative joint, and(3) an additional vaso-occlusive member attached to said additionalinsulative joint, and electrolytically disintegrating said link to leaveat least a portion of said assembly within said body cavity.
 16. Themethod of claim 15 further comprising the step of repeating said stepsof disposing said assembly at least partially into said body cavity andelectrolytically disintegrating said link to leave a plurality ofportions of said assembly within said body cavity.
 17. The method ofclaim 15 wherein said assembly is disposed at least partially into saidbody cavity through a catheter distal end, said catheter having a distalelectrode.
 18. The method of claim 17 wherein said catheter additionallycomprises a radiopaque marker.
 19. The method of claim 15 additionallycomprising the step of applying a positive electric current to saidassembly prior to electrolytically disintegrating said link to form athrombus within said body cavity.
 20. The method of claim 15 whereinsaid body cavity comprises an aneurysm.